This invention relates to the scanning of cinematographic film to produce electrical signals corresponding to the images stored on the film. These electrical signals may consist of analogue or digital video signals used to produce television pictures, video recordings or image data files.
Telecine or film scanning equipment used to produce such signals from cinematographic film have been known for many years, and are described for example in xe2x80x9cTV and Video Engineers Reference Bookxe2x80x9d Chapter 39 Butterworth and Heinemann ISBN 0-7506-1021-2. The techniques used to scan film for television applications employ either rastered light systems such as may be produced by a cathode ray tube and scanning system in conjunction with photosensitive detectors, or use a high intensity light source and solid state sensors such as line array or area array charge coupled devices. An example of current telecine equipment using the rastered light principle is the URSA(copyright) telecine manufactured by Cintel International Limited of Ware, Hertfordshire, England.
FIG. 1 shows a schematic diagram of the URSA(copyright) telecine which is a flying spot scanner. A cathode ray tube (1) produces a raster scan which is imaged onto the film (2) by lens (3), the film is moved past this imaging region at a constant speed by a capstan drive (4) and servo system (5) and the raster is adjusted to follow the film motion. The light passing through the film is modulated by the colour and density of the film at each location or pixel scanned, this light is analysed into it""s red green and blue primary colour components using dichroic mirrors (6) and then converted into electrical signals by photomultiplier tubes (7). The three electrical signals are then passed through various processing circuits (8) before being converted into a signal of television format by a frame store system (9). The scanned image may typically be 720 active pixels by 576 active lines this being converted into a standard interlaced television frame with a first field containing all the odd lines and a second field containing all the even lines.
The book xe2x80x9cfilm technology in post productionxe2x80x9d published by Butterworth-Heinemann ISBN 0-240-51463-7 describes the techniques used in post production of film using telecine equipment, in particular page 30 discusses non-linear editing. A film production which is intended for television use is typically transferred completely from the film negative with full grading and effects applied, and then the editing is done as a video production. This method involves unnecessary telecine time as the production film material is usually much longer than the final selected xe2x80x9ctakesxe2x80x9d. An alternative is to use non-linear editing where the production film material is transferred to video cassette ungraded or only roughly graded, this video material is first digitised then edited on the non-linear editing system. The Edit Decision List produced by the non-linear editing is then used by the telecine in a second transfer of the production film where only the required takes are transferred with full grading and effects and at television broadcast quality.
Whilst this latter method takes much less telecine time for the original transfer because minimal grading is needed, it does nevertheless use the telecine facility for a still considerable amount of time, and the telecine cannot be used for higher paying full quality graded work during that time. Further reduction in cost for this type of telecine work may be made by using a lower grade telecine or by scheduling the work outside normal working hours.
We have appreciated that a considerable further saving could be made if faster transfer rates could be achieved.
A proposal to provide faster scanning rates is put forward in GB-A-2,322,993. In this patent application, method of scanning film at a data rate greater than the real time data rate is proposed, using a high definition telecine, and providing an output at real time video data rate. The purpose of this proposed system is to use a high definition telecine to produce standard definition video data more quickly than standard definition video data produced from a standard definition telecine. In this regard, standard definition is defined as 625 picture lines, 576 of which are active with 720 active picture samples on each line at 25 frames per second, for European television, and 525 lines, of which 486 are active, with active 720 picture samples on each line at 30 frames per second for North American television. Whilst this proposal does increase transfer rates, a high definition telecine is required. It should be noted that there are slight variations of what is defined as standard definition. The NTSC RS170A standard is actually 29.94 frames per second, for example, and this and other slight variations are within the scope of standard definition.
We have appreciated that existing owners of standard definition telecines can benefit from faster transfer rates without needing to upgrade to a high definition telecine with the cost that this involves. We have further appreciated that existing standard definition telecines can be improved to provide a faster transfer rate. We have further appreciated that, for editing purposes, a lower than standard definition resolution is acceptable.
Accordingly, there is provided apparatus for configuring a standard definition raster scanner telecine having a film transport, raster scanner and light sensor, comprising means for causing the film transport of a standard definition telecine to move film past the light sensor of the telecine at a multiple of the standard definition rate; means for causing the telecine to scan film at the multiple of the standard definition frame rate but with a reduced resolution; whereby the configuration apparatus can configure a standard definition telecine to scan film at a faster than standard definition frame rate and produce a video data output at standard video data rate comprising video frames of lower than standard definition resolution.
Apparatus embodying the invention thus provides a telecine which may be used to feed a non-linear editing system, operating at a faster than standard definition film frame rate. This higher speed telecine output may be of reduced picture quality because it is used only for edit decision making and would not be incorporated in the final edited production. Standard definition in this document includes the two standards mentioned above, namely 625 picture lines, 576 of which are active with 720 picture samples on each line at 25 frames per second, for European television, and 525 lines, of which 486 are active, with 720 picture samples on each line at 30 frames per second for North American television. The invention is also applicable to any other standard definition telecine without requiring a high definition telecine as discussed above. As previously noted, xe2x80x9cstandardxe2x80x9d definition includes all variants of the adopted universal 525 and 625 line standards within the scope of the term, and is not limited to exactly the line numbers and frame rates above.
The invention is particularly suitable for the aforementioned URSA(copyright) telecine. Normal transfers of film take place at 24 or 25 film frames per second, with each frame consisting of 720 pixels by 576 lines of active video data (for the 625 line television system). These numbers are derived from a commonly used specification for the distribution of digital video signals (EBU Tech. 3267 or 3268 and CCIR recommendation 601), a similar specification for 525 line television systems is the ANSI/SMPTE 125M-1995.
In a preferred embodiment, the means for causing the telecine to scan film at the multiple of the standard definition frame rate comprises a controller for controlling the waveform of the scan. This has the advantage that the standard definition telecine is configured without requiring replacement of a large number of component parts. Preferably the controller comprises a look up table for providing scan addresses. This is a relatively straightforward modification to provide the desired scan pattern.
The controller preferably controls the waveform of each line scan and each frame scan to produce two sawtooth waveforms for each line pulse and four sawtooth waveforms for each frame pulse. This has the effect of doubling the line scan rate and quadrupling the frame scan rate without modifying the line and scan pulses.
The preferred embodiment includes means for producing the faster output signal using existing digital video interface standards and requiring a minimum of modification to existing telecine equipment.
The invention also provides a standard definition telecine comprising a film transport, raster scanner and light sensor, and further comprising means for causing the film transport to move film past the light sensor at a multiple of the standard definition frame rate, means for causing the telecine to scan film at the multiple of the standard definition frame rate but with a reduced resolution, whereby the telecine is so configured to scan film at a faster than standard definition frame rate and produce a video data output at standard video data rate comprising video frames of lower than standard definition resolution.
A telecine embodying the invention has the advantages noted above in relation to the configuration apparatus and may also have the preferred features set out above.
The invention also provides a method of scanning film using a standard definition raster scanner telecine, having a film transport, raster scanner and light sensor, comprising transporting film past the light sensor of the telecine at a multiple of the standard definition frame rate, scanning film at the multiple of the standard definition frame rate but with a reduced resolution, whereby the film is scanned at a faster than standard definition frame rate, and producing a video data output at standard video data rate comprising video frames of lower than standard definition resolution.
The preferred method is to cause the telecine to scan the film at a faster frame rate with reduced resolution and to pack several of these reduced resolution images into one frame of a standard digital television interface signal, this interface signal then couples to the non-linear editing equipment where the data would be repacked into a suitable format and stored in memory.
In an embodiment of the invention, the multiple of the standard definition frame rate could conceivably be a non-integer, however, this would cause complexities in subsequent handling of the image data. Accordingly, the multiple of the standard definition frame rate is preferably an integer, in particular the multiple is four.